I just "fixed" mine by applying a nice plate to the front
Strictly speaking you're supposed to have a front plate in MA but I really don't care. I've had various non-legal plates on the front of my previous cars and I've never had a problem. Fortunately it's only a a $35 slap on the wrist here.
I got the plate modeled after my fabulous rental car in Germany. That's why it's Hamburg and not Munich.